Sequential injection assemblies

Figure 12.2. Microcolumn flow-through manifolds for fractionation analysis in environmental solids (ti) continuous-flow system with either fraction collection or online detection (Jj) flow-injection setup with discrete injection of extractant (c) sequential injection system as assembled for fully automated sequential or single extractions. MC microcolumn, C coil, SP syringe pump, PP peristaltic pump, R reagent, D detector, W waste, SV selection valve, IV injection valve. (Adapted from Mir6 et al., 2005a.)...

Similar to FI systems, in-line coupling of a sequential injection network with suitable detectors renders a detailed insight into leaching kinetics. As a consequence of the discontinuous flow nature of SIA, the in-line hyphenation of microcolumn assays with ETAAS is relatively simple, because of the discrete, noncontinuous operation of the detector. On the other hand, interfacing the miniaturized flow assembly with continuously operating detectors such as FAAS, HG-AFS, ICP-AES and ICP-MS requires the incorporation of conventional sample injectors (e.g., solenoid valves, rotary valves) for discrete introduction into the detection instrument of metered leachate volumes. 

The Lab-on-Valve flow system resembles the sequential injection analyser but the main components are assembled on a multi-position valve. Exploitation of optical fibres permits spectrophotometric measurements to be performed very close to the main reaction coil. The compact geometry of the system makes it attractive for, e.g., in situ assays. For more details of this system, see 2.4.2. 

Sandwich techniques can also be implemented in a sequential injection analyser, as demonstrated by the spectrophotometric determination of nitrate and nitrite in natural waters [12]. The sample plug was set between two reagent plugs and the assembly was aspirated towards the holding coil of an ordinary sequential injection analyser. Two Griess reaction zones were established at both ends of the sample zone, and only one was... 

Figure 2 Universal flow-through cells in flow systems adaptable to absorbance, fluorescence, or chemiluminescence measurements. (A) Long path length water-core waveguide (B) LOV coupled to sequential injection schemes. In the figure, both cells are assembled for spectrophotometric detection. SP, syringe pump PP, peristaltic pump LED, light-emitting diode PD, photodetector.

FIGURE 2.6 Sequential injection lab-on-valve (SIA-LOV) assembly as coupled to column-separation systems using various interface modes. SP, syringe pump IV, injection valve HC, holding coil D, detector (xAC, microaffinity chromatograph. (Reprinted with permission from Miro, M., H. M. Oliveira, and M. A. Segundo. 2011. TrAC 30 153-164.)... 

Multi-colour moulding. This concept was devised for the automotive industry, specifically for rear light lens clusters in PMMA (polymethyl methacrylate). It involves a rotary mould assembly, with the different colours being injected sequentially from separate cylinders as the mould rotates. 

Especially in micro injection molded parts, the question of further processing always arises. The smallest parts are often difficult and cost-intensive to further process. Through the use of multi-component injection molding, such assembly operations can be prevented. In this method, two or more different materials can be injected either simultaneously or sequentially and thereby create a composite part. 

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